Dissolution of unirradiated UO2 fuel under oxidizing conditions: Evaluation of solubility (steady state) limiting factors (eq3/6)

Kaija Ollila

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

    3 Citations (Scopus)

    Abstract

    The solubility behavior of unirradiated UO2 pellets was studied under oxic, air-saturated conditions in deionized water, in NaHCO3 solutions and in two types of synthetic groundwater (25°C). The Allard groundwater represents natural fresh groundwater conditions at great depths in granite bedrock and bentonite groundwater simulates the effects of bentonite on granitic fresh groundwater. The release of uranium was measured during static batch dissolution experiments of long duration (6 years). A comparison was made with the theoretical solubility data calculated with the geochemical code, EQ3/6, in order to evaluate solubility (steady state) limiting factors. Various hypotheses for redox control (redox potential of the bulk solution or redox potential at the surface) were tested in the modeling calculations. The measured concentrations for uranium at steady-state in deionized water were equal to the solubility of schoepite (PO2 = 0.2 atm). In NaHCO3 solutions with lower carbonate concentrations (0.98-1.96 mmol/1) and in Allard groundwater they were close to the calculated solubilities of U at the U3O7/U3O8 redox potential. In bentonite groundwater, the results suggest the formation of a secondary phase with a lower solubility. Only uranium oxide with a crystal structure of uraninite (UO2- U3O7) was identified in all waters, when analyzing particulate material in the solutions after contact with UO2 pellets.
    Original languageEnglish
    Title of host publicationScientific Basis for Nuclear Waste Management XX
    EditorsWalter J. Gray
    Place of PublicationPittsburgh
    PublisherMaterials Research Society
    Pages549-556
    ISBN (Print)978-1-55899-369-3
    DOIs
    Publication statusPublished - 1997
    MoE publication typeA4 Article in a conference publication
    EventScience Basis for Nuclear Waste Management XX - Boston, United States
    Duration: 2 Dec 19966 Dec 1996

    Publication series

    SeriesMaterials Research Society Symposia Proceedings
    Volume465
    ISSN0272-9172

    Conference

    ConferenceScience Basis for Nuclear Waste Management XX
    CountryUnited States
    CityBoston
    Period2/12/966/12/96

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  • Cite this

    Ollila, K. (1997). Dissolution of unirradiated UO2 fuel under oxidizing conditions: Evaluation of solubility (steady state) limiting factors (eq3/6). In W. J. Gray (Ed.), Scientific Basis for Nuclear Waste Management XX (pp. 549-556). Materials Research Society. Materials Research Society Symposia Proceedings, Vol.. 465 https://doi.org/10.1557/PROC-465-549